Circularly Arced Koch Fractal Multiband Multimode Monopole Antenna
Circularly arced Koch fractal curve (CAKC) is originally proposed. Then, a novel wire dipole is formed with Ki-iterated CAKC. The dipole is experimentally studied for fractal electrical characteristics revealing. It manifests many unique properties, such as multiband resonance at odd times of half-wavelength. In particular, it unprecedentedly presents normal mode (0.5.λ) and axial mode (1.5.λ) simultaneously. Thus, K2 CAKC wire is configured into folded monopole with circular disc ground for omni-directional and directive radiation. Five matched bands (S11≤-10 dB) are obtained within 1 GHz-10 GHz, of which f1=1.31 GHz, f2=3.14 GHz, f3=3.63 GHz, f4=4.65 GHz, and f5=7.71 GHz. Compared with conventional wire monopole (0.25.λ), this fractal monopole shows 31% height reduction. It has dipole-like patterns at f1 and f2, endfire patterns at f3 and f4 with high gain (10 dBi), and off-endfire patterns at f5. Moreover, the fractal antenna possesses compactness, lightweight, simplicity, and low cost. So, it is an attractive candidate for multiband and multifunction antennas, such as satellite antennas, of which omni-directional normal mode and directive axial mode are needed for beaconing and communication respectively.